DE102006042554A1 - Method and system for continuously transmitting encrypted data of a broadcast service to a mobile terminal - Google Patents

Abstract

A method for continuously transmitting encrypted data of a broadcast service from service access networks having different key hierarchies to a mobile terminal (BEG), the mobile terminal (BEG) changing from a first service access network (DZN-A) of which the mobile terminal (BEG) receives the data of the broadcast service encrypted with a first data content encryption key (MTK; TEK; SK) to a second service access network (DZN-B) from which the mobile terminal (BEG) the data of the same broadcast service encrypted with a second data content encryption key (MTK; TEK; SK) receives a key (SEK; PEK; MSK; BAK) encrypted with a subscriber-specific key (MUK; K-PUB; TK) of the first service access network (DZN-A) of the key hierarchy second service access network (DZN-B) receives.

Description

The The invention relates to a method and system for continuous transmission from encrypted Data of a broadcast service to a mobile terminal, which from a service access network having a first key hierarchy to another service access network with a second key hierarchy replaced.

at In particular, point-to-multipoint data services become multimedia data, such as audio and video data from a server of a Content provider or service provider to a terminal. Is it the terminal to a mobile device or user terminal BEG, such as a mobile phone or a laptop, the data transfer takes place from the server of the service provider a service access network DZN or Service Access Network and from there via a Radio interface to the mobile terminal. There are different multicast or Access technologies are known, each with different procedures to authenticate and register participants and control access to the multicast or broadcast services. examples for Such known broadcast technologies are those in the 3GPP (Third Generation Partnership Project) specified multimedia broadcast and Multicast System (MBMS), DVB-H (Digital Video Broadcast to Handhelds) system based on the Internet Protocol IP, abbreviated DVB-H IPDC (DC: Data Cast), the 3GPP2 BCMCS (Third Generation Partnership Project 2-Broadcast Multicast Service) and the OMA BCAST (Browser and Content Broadcast) of the standardization body the Open Mobile Alliance (OMA). These different access technologies to provide broadcast or multicast services to mobile devices especially different key hierarchies for encrypting Data transmission links.

The different service access networks have partially overlapping Cover areas, so that a mobile terminal of a Coverage area of a first service access network to a transmission area of a second service access network with a different access technology can move. Mobile devices or user terminals BEG can support different access technologies to the appropriate ones To receive broadcast services.

The from the standardization committee Third Generation Partnership Project (3GPP) Specified Multimedia Broadcast Multicast System (MBMS) Realizes IP-based point-to-multipoint data services in 3GPP mobile networks (3GPP MBMS ARC). Examples of such data services are audio, video and voice services (streaming services), but also services with which Help pictures and texts to terminals be broadcast (download and so-called Carousel Services). In addition to the Radio Access Network (RAN), the serving and Gateway GPRS Support Nodes (SGSN and GGSN) are the user terminal (User Equipment - UE) and the broadcast multicast service center (BM-SC) the most important ones MBMS network components. The actual data content is the BM-SC provided by a content provider (ContProv).

MBMS Streaming services that prevent unauthorized use should, can encrypted using the Secure Realtime Transport Protocol (SRTP) and against change protected become (integrity protection). This function is taken over by the BM-SC (3GPP MBMS SEC). This requires cryptographic key material at the BM-SC as well as at the authorized user terminals (UE) to disposal be put. For efficiency reasons a given MBMS streaming service may not work for each one single terminal separately protected and broadcasted; rather, BM-SC and the authorized ones share terminals so-called MBMS Traffic Keys (MTK). MTKs change frequently but not specific to a specific terminal.

In order to MTKs are not even on their way from the BM-SC to the mobile devices BEG to be intercepted can, they are encrypted using so-called MBMS Service Keys (MSK). MSKS are much more durable than MTKs and therefore less often than Transmitted MTKs to the UEs become. Of course have to also MSKs during their transport to the BEGs are protected against eavesdropping. This will be with help so-called MBMS User Keys (MUK). In difference to MTKs and MSKs, a single MUK is only valid for a single BEG terminal. The means that an MSK that is sent encrypted with a specific MUK will, even only from the terminal BEG decrypted who knows this MUK.

MUKS be between the terminal BEG and the BM-SC with the help of the so-called Generic Bootstrapping Architecture (GBA) negotiated. The GBA is about a method specified by the 3GPP to distinguish between the terminal BEG and the mobile network anyway existing security relationship a security relationship between the terminal BEG and a so-called Derive Network Application Function (NAF) (3GPP GBA). In connection with MBMS the BM-SC the role of this NAF.

Regardless of MBMS share the end BEG and a Home Subscriber Server (HSS) in the home network of the BEG a long-lived, secret key K, which is stored on the Universal Integrated Circuit Card (UICC) of the BEG and in a database of the HSS server. Based on this key K, the BEG terminal and the GBA component called Bootstrapping Server Function (BSF) authenticate each other. The HSS server supplies the BSF with the relevant, in part terminal-specific, data (Zh, reference point). In connection with this authentication, the terminal BEG and BSF derive a secret key Ks, which serves to generate a key Ks_NAF, which depends on the identity of the NAF. On request, the bootstrapping server BSF notifies the NAF (in the MBMS example: the BM-SC) of this Ks_NAF (Zn reference point), so that subsequently the terminal and NAF share a secret cryptographic key, namely Ks_NAF. Overall, based on the existing security relationship between terminal and mobile network (key K), a security relationship between the terminal UE or BEG and the NAF is established (key Ks_NAF).

at MBMS forward terminal and BM-SC from Ks_NAF a so-called MBMS Request Key (MRK), with the help of the terminal Authenticated at the BM-SC (eg reference point). This gives the UE the authorization to receive a specific MBMS service. These Authorization causes the BM-SC to provide the terminal with an MBMS Service Key (MSK) sent using an MBMS user key derived from MRK (MUK) encrypted is. As mentioned above, is now just the device, that owns the MRK-derived MUK, able to access the MSK decrypt. With the help of MSK, however, the terminal can be the non-terminal-specific MBMS Traffic Keys (MTK) and thus the entire, SRTP-protected MBMS streaming service decipher and integrity check the data. Consequently The security of 3GPP MBMS relies on the following key hierarchy:

Long-lasting 3GPP key K

• - only the BEG and an HSS in the home network of the BEG or UE known
• - Used for GBA authentication between BEG and BSF

GBA key Ks and Ks_NAF

• - Ks is related to the GBA authentication procedure derived between BEG and the home network of the BEG and serves the Generation of the key Ks_NAF
• - In MBMS, the keys MRK and MUK are derived from Ks_NAF

MBMS Request Key (MRK)

• - from BEG and BM-SC derived from Ks_NAF
• - serves for the authentication and authorization of the BEG against NAF = BM-SC at service registration

MBMS User Key (MUK)

• - derived from Ks_NAF
• - serves for the BEG-specific encryption of MSK

MBMS Service Key (MSK)

• - from BM-SC for generated a specific service
• - serves for encryption MTKs transport to the BEGs
• - is longer valid as MTKs

MBMS Traffic Keys (MTK)

• - from BM-SC generated keys for protection (encryption and integrity protection) an MBMS service
• - Not BEG-specific
• - become encrypted with the help of MSK transferred to BEGs

The Standardization Panel Digital Video Broadcast (DVB) has specifications issued the video broadcast services to mobile devices BEG (DVB to Handhelds - DVB-H) Define on the basis of the Internet Protocol (IP): IP Data Cast over DVB-H, abbreviated IPDC / DVB-H (DVB IPDC). The DVB-H system not only has a unidirectional Broadcast channel, but also over one optional bidirectional interaction channel (Interactive Channel), the z. B. can be realized by a 3GPP mobile network.

The DVB-H document "IP Data Cast over DVB-H: Service Purchase and Protection "(DVB IPDC SPP) two different security systems for DVB-H services:

System 1: Open Security Framework (OSF)

• - recommends the encryption Broadcast Services at the Data Content Level (ISMACryp)

System 2: 18 Crypt

• - recommends the encryption broadcast services at the transport layer (SRTP) or at the network level (IPSec)

User terminals BEG, which comply with the SPP specification must use all three encryption methods Support (ISMACryp, SRTP, IPSec), and implement at least one of the two systems.

1 shows a DVB-H model for the protection of data content in broadcast services according to the prior art.

First, the terminal BEG (Device) requires a long-lived key K, which is unique to this device. Such a key is usually already in the purchase on the device or on a smart card, which is inserted into the device. This key forms the foundation for the safety of the four layers in 1 are shown.

On the top layer (Registration) authenticates the device with the help of a unique key K and registers for a specific broadcast service. Based on a successful Authentication and registration receives the terminal one cryptographic keys (Rights Encryption Key) necessary to receive the service. Of the Rights Encryption Key is using the device-specific key K encrypted so that only the end gets, that this key K, can decrypt the Rights Encryption Key.

On the second layer (Rights Management) receives the terminal a longer Time valid service Encryption Key (SEK) using a Key Management Message (KMM) transmitted to the terminal becomes. The SEK is clearly for the broadcast service, not for the terminal. The Rights Encryption is used to encrypt SEK. In its functionality SEK is comparable to the 3GPP MBMS Service Key (MSK).

On the third layer (key stream) transport so-called key Stream Messages (KSM) Short-lived Traffic Encryption Keys (TEK) over the broadcast channel to the terminals. The TEKs are encrypted with the Service Encryption Key (SEK), which previously transferred to the second layer has been. At the bottom layer (Content / Service Protection) is the broadcast service - encrypted with Help of TEKs - about the Broadcast channel broadcast.

With Help of his device specific key K can be the terminal decrypting the Rights Encryption Key, thus turning the SEK and subsequently the frequently changing TEKs. This is the registered and therefore authorized terminal BEG able to encrypted Broadcast service in plain text.

This in 1 Model presented describes the technical realization of the protective measures of IPDC / DVB-H at a very general level. This is due to the fact that this model in [DVB IPDC SPP] represents the two very different systems Open Security Framework and 18Crypt uniformly. On the other hand, in [DVB IPDC SPP] the technical realization of layers 1-3 (Registration, Rights Management and Key Stream) is not explicitly specified for the Open Security Framework, but left open - in contrast to the 18Crypt system, for which all layers are defined were.

The 18Crypt System is based on digital rights management procedures (DRM) specified by the Open Mobile Alliance (OMA) [OMA DRM]. It uses as a unique device key a public encryption key whose Binding to a specific device is guaranteed by a digital certificate. For authentication and registration of the device on the registry layer checks one like that Rights Issuer (RI), the validity of the digital device certificate. If successful, the RI sends the device to Rights Management Layer to a so-called rights object (RO). This RO contains one Service or Program Encryption Key (SEK / PEK), which uses the verified, public Device key is encrypted. Only the device specified in the digital certificate has the corresponding private device key. It is therefore the only device that the encrypted SEK or PEK in that legal entity RO can decrypt.

Next SEK or PEK contains the legal object RO usually still the description of rights, the device granted be in relation to the data content of the broadcast service for which the device has registered (eg: Video may be played five times from the end device become). On the terminal is against change protected Program (DRM Agent) responsible for the decryption of SEK or PEK, for compliance with the rights that the device has in relation to a particular Data content granted were, and for the protection of SEK or PEK against unauthorized access. The SEK or PEK is used on the key stream layer to change frequently Encrypting and decrypting traffic encryption keys (TEK).

In mobile networks conforming to the Third Generation Partnership Project 2 (3GPP2) standards, IP-based broadcast and multicast services are implemented using the Broadcast Multicast Service (BCMCS) [3GPP2 BCMCS]. 3GPP2 user terminals (Mobile Station - MS) consist of a User Identity Module (UIM) and the actual Mobile Device (Mobile Equipment). ME). A UIM can either be firmly attached to the ME or removable (Removable UIM - R-UIM). While UIMs have a protected memory area but little computing power, the ME mobile device has more computing power but no protected memory.

To the encode The broadcast / multicast data content can be secure real-time transport Protocol (SRTP). The keys that serve as input for SRTP encryption are called short-term keys (SK). As well as 3GPP MBMS traffic Keys (MTK) change frequently, But they are not encrypted like MTKs to the mobile stations MSs sent. Instead, it becomes an encrypted broadcast access key (BAK) together with a random number SK_RAND to the mobile terminals or MSs sent, and the mobile devices BEG or MS calculate BAK and SK_RAND the key SK. BAK is a non-MS or UIM-specific key; much more is BAK for One or more IP multicast message flows are valid. BAKs are taken from the network component BAK Distributor (BAKD) generated.

On his way to a mobile terminal BEG or MS becomes a BAK encrypted using a Temporary Encryption Key (TK). Everyone TK depends on a random number TK_RAND and a so-called Registration Key (RK). RK is unique to each UIM and only the one concerned UIM and the network component known to be responsible for the generation of TKs is (Subscription Manager - SM). The mobile device receives together with the TK encrypted BAK also the random value TK_RAND. Only the mobile device that runs on its UIM over the RK has, which was used to generate TK, can then with the help from TK_RAND the key Derive TK. TK serves the mobile terminal to decrypt BAK. With the help of BAK and SK_RAND the MS or the BEG can then SK and decrypt the encrypted multicast data.

The Security of 3GPP2 BC MCS is based on the following key hierarchy:

Registration Key (RK)

• - Clearly for every UIM
• - Just UIM and the Subscription Manager (SM)

Temporary Encryption Key (TK)

• - Derived from RK and a random number TK_RAND
• - Serves for encryption a broadcast access key (BAK)
• - MS receives TK_RAND together with the encrypted BAK
• - Just MS with the correct RK can calculate TK using TK_RAND

Broadcast Access Key (BAK)

• - Becomes from the BAK Distributor (BAKD) for generates one or more IP multicast message flows
• - MS receives BAK encrypted with TK together with a random number SK_RAND

Short-term keys (SK)

• - key to encode (SRTP) of broadcast / multicast data
• - Becomes not sent to MS, but calculated by MS from BAK and SK_RAND

The Broadcast (BCAST) Subset of the Browser and Content (BAC) Workgroup standardized by the standardization body Open Mobile Alliance (OMA) a so-called enabler for mobile Broadcast Services over Networks with a uni-directional broadcast channel (eg DVB-H) and an optional bi-directional unicast channel (eg 3GPP) [OMA BCAST ARC]. There are functions like service Guide, File Distribution, Stream Distribution, Service Protection, Content Protection, Service Interaction, Service Provisioning, Terminal Provisioning and Notification specified.

In In particular, OMA BAC BCAST supports the current design specifications 3GPP MBMS, DVB-H IPDC and 3GPP2 BCMCS as broadcast distribution systems. The protection of broadcast services (Services) and Content is defined in [OMA BCAST SCP] and offers three characteristics on, namely a DRM profile based on the OMA specifications for Digital Rights Management [OMA DRM] is based and two smartcard profiles Base of 3GPP (U) SIM or 3GPP2 (R) UIM.

by virtue of different access technologies and in particular due to the different key hierarchies, used in the various access technologies, exists when a mobile terminal BEG changes from a first service access network a second service access network has the problem that the data transmission is interrupted.

The change from one service access network to another service access network can either be done by moving a mobile terminal from the coverage area of a first service access network into the coverage area of a second service access network or the subscriber switching to a first service network to another service access network.

It is therefore an object of the present invention, a method and a system for transmitting from encrypted Data to create a broadcast service, providing continuous data transmission ensure data from a broadcast service to a mobile terminal, even if the service access network is changed.

These The object is achieved by a Process with the features specified in claim 1 and by a system having the features specified in claim 19 solved.

The Invention provides a method of continuous transfer from encrypted Data of a broadcast service of service access networks that are different key hierarchies to a mobile terminal (BEG), being the mobile terminal (BEG) when switching from a first service access network DZN-A, from which the mobile terminal BEG the data of the broadcast service with a first data content encryption key MTK, TEK, SK receives encrypted, too a second service access network DZN-B, of which the mobile terminal BEG the Data of the same broadcast service with a second data content encryption key MTK, TEK, SK encrypted receives one with a subscriber-specific key MUK, K-PUB, TK of the first Service Access Network DZN-A encrypted key of key hierarchy of the second service access network DZN-B.

at a preferred embodiment the method according to the invention the subscriber-specific key (MUK, TK) will follow to an authentication of the mobile terminal (BEG) at an access control server (ZKS-A) of the first service access network (DZN-A) generated.

at an embodiment the method according to the invention feature the mobile device (BEG) and the access control server (ZKS-A) of the first service access network (DZN-A) both about the subscriber-specific key.

at a preferred embodiment the method according to the invention receives the mobile device BEG the data of the broadcast service with the first data content encryption key of a first access control server ZKS-A of the first service access network DZN-A.

at a preferred embodiment the method according to the invention receives the mobile device BEG the data of the broadcast service with the second data content encryption key of a second access control server ZKS-B of the second service access network DZN-B.

at a preferred embodiment the method according to the invention becomes the key encrypted with the subscriber-specific key of the access control server ZKS-A of the first service access network DZN-A to the mobile device BEG transferred and through the mobile device BEG by means of the mobile terminal known participant specific key decrypted.

at an embodiment the method according to the invention decrypts the mobile device BEG by means of the decrypted Key the second data content encryption key to so that those received by the second access control server ZKS-B and encrypted with the second data content encryption key To decrypt data from the broadcast service.

at an embodiment the method according to the invention calls for the mobile device BEG a change from the first service access network DZN-A to the second Service access network DZN-B from the access control server of the first Service access network ZKS-A by means of a request message to.

at an embodiment the method according to the invention the request message has a subscriber identity, a identity the access control server ZKS-B of the second service access network DZN-B and an identity the broadcast service on.

at an embodiment of the inventive method transmits the access control server ZKS-A of the first service access network DZN-A an access request message to the access control server ZKS-B of the second service access network DZN-B, which is the subscriber identity, the identity of the broadcast service and an identity the access control server ZKS-A of the first service access network DZN-A contains.

at an embodiment of the inventive method transmits the access control server ZKS-B of the second service access network DZN-B an access acknowledgment message to the access control server ZKS-A of the first service access network DZN-A back, which the participant identity, the identity the broadcast service and a key of the key hierarchy of the second service access network.

In one embodiment of the invention In accordance with the method, the access control server ZKS-A of the first service access network DZN-A transmits an ACK message to the mobile terminal BEG, which contains an identity of the second access control server ZKS-B and an identity of the broadcast service.

at an embodiment of the inventive method transmits the access control server ZKS-A of the first service access network DZN-A with the subscriber-specific key encrypted key the second key hierarchy in a message to the mobile device BEG.

at an embodiment the method according to the invention the first service access network DZN-A is replaced by a 3GPP, a 3GPP2 or a DVB-H service access network.

at an embodiment the method according to the invention the second service access network DZN-B is replaced by a 3GPP, a 3GPP2 or a DVB-H service access network.

at an embodiment the method according to the invention the change from the first service access network DZN-A to the second service access network DZN-B through the access control server ZKS-A of the first service access network DZN-A automatically performed when itself the mobile terminal BEG from a transmission range of the first service access network DZN-A moved out.

at an embodiment the method according to the invention becomes the mobile terminal BEG formed by a mobile phone, a laptop or a PDA device.

at an embodiment the method according to the invention The data received by the mobile terminal BEG are transmitted through Multimedia data formed.

The The invention also provides a system for continuous transmission from encrypted Data of a broadcast service to a mobile terminal BEG of Service access networks DZN, the different key hierarchies having a first access control server ZKS-A of a first Service access network DZN-A, which is a first key hierarchy wherein the mobile terminal BEG the data of the broadcast service with a first data content encryption key from the first access control server ZKS-A of the first service access network DZN-A encrypted receives a second access control server ZKS-B a second service access network DZN-B, which is a second key hierarchy wherein the mobile terminal BEG the data of the broadcast service with a second data content encryption key of the second access control server ZKS-B of the second service access network DZN-B encrypted receives the mobile terminal BEG on a change from the first service access network DZN-A the second service access network DZN-B one with a subscriber-specific key of the first service access network DZN-A encrypted key of key hierarchy of the second service access network DZN-B receives.

The The invention further provides an access control server ZKS for providing a continuous broadcast service for a mobile terminal BEG, wherein the access control server ZKS when changing the mobile terminal BEG from a service access network DZN of the access control server ZKS to another service access network DZN` one with a subscriber-specific key of Service access network DZN encrypted key of the second service access network DZN-B transmits to the mobile terminal BEG.

in the Other preferred embodiments the process of the invention and of the system according to the invention for continuous transmission from encrypted Data of a broadcast service with reference to the attached figures In order to explain features essential to the invention described.

It demonstrate:

1 : A layered model of a conventional access technology for protecting data content in broadcast services of the prior art;

2 a block diagram of a possible embodiment of the system according to the invention for the continuous transmission of encrypted data;

3 a signal diagram for explaining a first embodiment of the method according to the invention for continuously transmitting encrypted data of a broadcast service;

4 FIG. 4 is another signal diagram for explaining a second embodiment of the method according to the invention for continuously transmitting encrypted data of a broadcast service; FIG.

5 FIG. 3 is a further signal diagram for explaining a third embodiment of the method according to the invention for continuously transmitting encrypted data of a broad cast service;

6 FIG. 4 is another signal diagram for explaining a fourth embodiment of the method according to the invention for continuously transmitting encrypted data of a broadcast service; FIG.

7 FIG. 2 is another signal diagram illustrating a fifth embodiment of the method according to the invention for continuously transmitting encrypted data of a broadcast service; FIG.

8th FIG. 2: another signal diagram to illustrate a sixth embodiment of the method according to the invention for continuously transmitting encrypted data of a broadcast service.

How to get out 2 can recognize the system according to the invention for continuously transmitting encrypted data of a broadcast service from at least two service access networks DZN or service access networks. One of these service access networks contains several base stations BS, via which a mobile terminal or user terminal BEG can exchange data with the service access network DZN via an air interface. The base stations BS of the service access network DZN are connected, for example, to a gateway GW of the service access network. The gateway connects the service access network DZN with a core network CN. In this CN there is an access control server ZKS, which controls the access to multicast or broadcast services in its respective area of responsibility. For example, the access control servers ZKS are connected to a content provider server CPS, which provides multimedia data for a multicast or broadcast service. The broadcast services can be, for example, the provision of audio, video or voice services (streaming services), but also, for example, services that can be used to broadcast images and text to the mobile devices BEG.

at the system according to the invention can the two service access networks DZN-A, DZN-B different access technologies exhibit. For example, the first service access network may be DZN-A to be a 3GPP, 3GPP2 or DVB-H service access network. In the same way This may also be the case with the second service access network DZN-B to be a 3GPP, 3GPP2 or DVB-H service access network. The system according to the invention allows a seamless transition of the mobile terminal BEG of the area of responsibility the first access control server ZKS-A, d. H. from the service access network DZN-A, to the area of responsibility the second access control server ZKS-B, d. H. to the service access network DZN-B. A change from a first service access network DZN-A to the second service access network DZN-B, for example, by the Access Control Server ZKS be automatically performed when a mobile terminal BEG from the transmission range of the base station BS of the first service access network DZN-A moved out and in the transmission area of the base station BS of the second service access network DZN-B arrives. These are for example signal strength monitors the exchanged messages and the change through the access control server ZKS automatically caused when the signal amplitudes in the first service access network DZN-A fall below a certain threshold. Alternatively, you can the change from one service access network DZN-A to another Service access network DZN-B, which is the same or an alternative Access technology by the participants of the mobile terminal BEG be initiated by at the mobile terminal BEG a appropriate change sets.

If, for example, a subscriber of a mobile terminal BEG, for example a mobile telephone, wants to see on his display a movie or a television movie which is offered by the content provider CPS, he can log on to the first service access network DZN-A for this broadcast service. First, he goes through an authentication procedure and receives according to the key hierarchy of access technology of the service access network DZN-A keys to decrypt the encrypted media data, which allow it to decrypt when receiving the encrypted media data this. In this case, these keys are preferably in turn transmitted encrypted to prevent eavesdropping. Upon completion of this procedure, the mobile terminal BEG can receive and decrypt the data stream via the first service access network DZN-A. If the subscriber with his mobile terminal outside the range of the first service access network DZN-A now enters the transmission area of another service access network DZN-B, which has, for example, a different access technology, the system according to the invention provides a continuous change which is not consciously noticeable to the subscriber from the first service access network DZN-A to the second service access network DZN-B without the user terminal BEG and the second access control server undergoing a complete, complex and user-consuming or subscriber-consuming service registration. In the same way, a change from a first service access network DZN-A to a service access network DZN-B, if provided the subscriber makes a corresponding switchover at his mobile terminal BEG, for example in order to save charges, provided that data transmission via the second service access network DZN-B is more cost-effective for him.

The mobile terminal BEG of the subscriber receives first the data of the broadcast service, such as the one you want Films, with a first data content encryption key of the first access control server ZKS-A of the first service access network DZN-A encrypted.

at a change of the mobile terminal BEG from the first service access network DZN-A to the second service access network DZN-B receives the mobile device BEG one with a subscriber-specific key of the first service access network encrypted key of the second service access network DZN-B.

Subsequently or after the change receives then the mobile device BEG the data of the same broadcast service with a second Data content encryption key of the second access control server ZKS-B of the second service access network DZN-B in encrypted Shape.

at the system according to the invention are the two access control servers ZKS-A, ZKS-B via a common interface or interface INT connected to each other and exchange messages with each other. These messages contain data such as identifiers for the mobile terminal BEG, for the subscriber myself, for the area of responsibility the first and second access control server ZKS-A, ZKS-B, for a or several broadcast services as well as cryptographic keys and Details of their validity.

at the method according to the invention The mobile terminal BEG first authenticates itself to the first access control server ZKS-A of the first service access network DZN-A.

Subsequently, the first receives Access control server ZKS-A a key directly from the second Access control server ZKS-B or indirectly from a key server, to which the second access control server ZKS-B previously transmitted this key Has.

In encrypted another step the first access control server ZKS-A with the obtained key with Help a secret, symmetric key, such as a subscriber-specific key, which only the mobile terminal BEG and the first access control server ZKS-A of the first service access network DZN-A know and on the basis of the authentication process of the mobile terminal BEG was generated at the first access control server ZKS-A. Alternatively encrypted the first access control server ZKS-A with the received key with Help of a public, asymmetric key, its affiliation to the mobile terminal BEG from the first access control server ZKS-A during the authentication of the mobile terminal BEG is checked.

Subsequently, the first transfers Access control server ZKS-A with the secret symmetric key or with the public asymmetric key encrypted key to the mobile terminal BEG.

The mobile terminal BEG decrypted the encrypted key with the help of the secret symmetric key or with the help of the the public asymmetric key belonging, secret, asymmetric key, with the help of such decrypted key the keys to encoding decrypt the data content of the broadcast service.

The following 4 to 8th show six different embodiments of the inventive method for continuously transmitting encrypted data of a broadcast service of service access networks DZN with different key hierarchies to the mobile terminal BEG.

The six embodiments according to 3 to 8th show different case constellations, where the service access networks DZN-A, DZN-B is a 3GPP, 3GPP2 or a DVB-H service access network.

At the in 3 In the case illustrated, the mobile terminal BEG is changed from a 3GPP service access network to a DVB-H service access network.

After a successful pass of the 3GPP GBA authentication procedure, the user terminal BEG and the access control server ZKS_A are in possession of the key Ks_NAF, from which the keys MBMS Request Key (MRK) and MBMS User Key (MUK) are derived. With the help of MRK, BEG authenticates itself to ZKS_A and registers for the multicast service ID_SVC, which falls under the responsibility of ZKS_A. Since BEG has successfully registered with ZKS_A for the multicast service ID_SVC, ZKS_A sends the MBMS service key (MSK) belonging to this service to BEG, encrypted using BEG's MBMS User Key (MUK). With the help of MUK, BEG can send the message Encrypt [MUK] (MSK) Decrypt and thus also the MBMS Traffic Keys (MTK), which - encrypted with the help of MSK - are sent to the user terminals. The decrypted MTKs now allow the BEG to decrypt the multicast service (content) that is encrypted using these MTKs and identified by ID_SVC. The BEG initiates a transfer from the area of responsibility of the ZKS_A to the ZKS_B by sending a transfer request (HORequest = Handover Request) to ZKS_A. This message advantageously contains the identity ID_BEG of the user terminal BEG or ID_USER of the user, the identity ID_ZKS_B of ZKS_B, the identity ID_SVC` of a multicast service in the area of responsibility of ZKS_B, as well as possibly further relevant data.

In favor of of the user terminal sends ZKS_A an access request to ZKS_B, which advantageously next to the identities ID_BEG, ID_USER, ID_SVC` and ID_ZKS_A may contain other relevant data. Based on the fact that BEG already successfully authenticates at ZKS_A and is registered, ZKS_B can without a re-authentication and Registering the BEG will decide if he has BEG access to the multicast service Grant ID_SVC` want or not. granted ZKS_B the user terminal BEG access to the desired Multicast service ID_SVC`, he sends an access granting message (Access Accept) to ZKS_A along with the service or programs Encryption Key (SEK / PEK) leading to the desired multicast service ID_SVC` belongs. Because ZKS_B is the user terminal BEG access to the desired Granted multicast service ZKS_A sends a handover grant message (HOAccept = Handover Accept) to BEG. This message contains benefits the identities ID_ZKS_B and ID_SVC` of the access control server ZKS_B or the desired one Service.

ZKS_A sends the key to BEG SEK or PEK, which it contained from ZKS_B, encrypted with MUK. Since the BEG the key MUK knows, it can decrypt SEK or PEK. Because of his knowledge from SEK or PEK BEG is now able to encode those encrypted with SEK or PEK Decrypt Traffic Encryption Keys (TEKs). The decrypted TEKs now allow the BEG to use the multicast service (Content) to decode, which is encrypted with the help of these TEKs and by ID_SVC` is identified.

4 shows a second case constellation in which a mobile terminal BEG changes from a DVB-H service access network to a 3GPP service access network.

With the help of its public key certificate, BEG authenticates itself to ZKS_A and registers for the multicast service ID_SVC, which falls under the responsibility of ZKS_A. Since BEG has successfully registered for the multicast service ID_SVC at ZKS_A, ZKS_A sends the service or programs belonging to this service Encryption Key (SEK / PEK) to BEG. In this case, SEK / PEK is contained in a rights object RO and is present there in encrypted form. For encryption the public key K_PUB of BEG is used. With the help of his private device key K_PRIV, BEG can decrypt the key SEK or PEK and thus also the traffic encryption keys (TEK), which are sent encrypted with the help of SEK or PEK to the user terminals. The decrypted TEKs now allow the BEG to decrypt the multicast service (content) that is encrypted using these TEKs and identified by ID_SVC. The BEG initiates a transfer from the area of responsibility of the ZKS_A to the ZKS_B, in which it sends a transfer request (HORequest = Handover Request) to ZKS_A. This message advantageously contains the identity ID_BEG of the user terminal or ID_USER of the user, the identity ID_ZKS_B of ZKS_B, the identity ID_SVC 'of a multicast service in the area of responsibility of ZKS_B, as well as possibly further relevant data. In favor of the user terminal, ZKS_A sends an access control request (AccessRequest) to ZKS_B, which, in addition to the identities ID_BEG, ID_SVC 'and ID_ZKS_A, may also contain further relevant data. Based on the fact that BEG is already successfully authenticated and registered with ZKS_A, ZKS_B can decide without a renewed authentication and registration of the BEG, whether or not it wants to grant BEG access to the multicast service ID_SVC '. If ZKS_B grants the user terminal access to the desired multicast service ID_SVC ', it sends an access grant message (ACCESSAccept) to ZKS_A together with the MBMS service key MSK belonging to the desired multicast service ID_SVC'. Since ZKS_B has granted the user terminal BEG access to the desired multicast service, ZKS_A sends a handover accept message (HOAccept = Handover Accept) to the BEG. This message advantageously contains the identities ID_ZKS_B and ID_SVC 'of the access control server ZKS_B or the desired service. ZKS_A sends to BEG the key MSK it contained from ZKS_B, encrypted using K_PUB as part of a rights object RO. Using its private device key K_PRIV, BEG can decrypt the key MSK. Based on its knowledge of MSK, BEG is now able to decrypt the MSK encrypted MBMS traffic keys (MTKs). The decrypted MTKs now allow the BEG to decrypt the multicast service (Content ') that verifies with the help of these MTKs is keyed and identified by ID_SVC '.

5 shows a third case constellation in which a mobile terminal BEG changes from a 3GPP service access network to a 3GPP2 service access network.

To a successful pass of the 3GPP GBA authentication procedure are the user terminal BEG and the access control server ZKS_A in the possession of the key Ks_NAF, from the keys MBMS Request Key (MRK) and MBMS User Key (MUK). With the help of MRK, BEG authenticates itself to ZKS_A and registers for the Multicast service ID_SVC, which falls under the scope of ZKS_A falls. Since BEG for successfully registered the multicast service ID_SVC with ZKS_A, ZKS_A sends the MBMS Service Key (MSK) belonging to this service to BEG, and encrypted using the BMS MBMS User Key (MUK). With the help of MUK can BEG decrypt the message ENcrypt [MUK] (MSK) and thus also the MBMS Traffic Keys (MTK) - encrypted with Help from MSK - on the user terminals be sent. The decrypted MTKs now allow the BEG to use the multicast service (Content) to decode, encrypted using these MTKs and ID_SVC is identified. The BEG initiates a transfer from the area of responsibility of the ZKS_A to the ZKS_B in which there is a transfer request (HORequest = Handover Request) to ZKS_A. This message contains benefits the identity ID_BEG of the user terminal or ID_USER of the user, the identity ID_ZKS_B of ZKS_B, the identity ID_SVC 'of a multicast service in the area of responsibility from ZKS_B, as well as possibly further relevant data. In favor of of the user terminal ZKS_A an access control request (AccessRequest) to ZKS_B, the beneficial next to the identities ID_BEG, ID_USER, ID_SVC 'and ID_ZKS_A may contain further relevant data. Based on the fact that BEG is already successfully authenticated and registered with ZKS_A, can ZKS_B without a re-authentication and registration of the BEGes decide whether to grant BEG access to the multicast service ID_SVC ' or not. granted ZKS_B the user terminal Access to the desired Multicast service ID_SVC ', so he sends an access grant message (AccessAccept) to ZKS_A together with the Broadcast Access Key (BAK), the one to the desired Multicast service ID_SVC 'belongs. Because ZKS_B the user terminal BEG access to the desired Granted multicast service ZKS_A sends a handover grant message (HOAccept = Handover Accept) to BEG. This message advantageously contains the identities ID_ZKS_B and ID_SVC 'of the access control server ZKS_B or the desired Service. ZKS_A sends to BEG the key BAK, which it contains from ZKS_B has, and indeed encrypted with MUK. Because the BEG is the key MUK knows, it can decrypt BAK. The BEG receives the multicast service identified by ID-SVC 'and using short-term Keys (SK) encrypted is. In addition to the encrypted Receives multicast service BEG also the unencrypted Random SK_RAND. Using BAK and the random numbers SK_RAND The BEG can calculate the short-term keys SK and thus decrypt the multicast service (Content ').

6 shows another case constellation in which a mobile terminal BEG changes from a 3GPP2 service access network to a 3GPP service access network.

The BEG authenticates itself to the ZKS_A using an authentication key (Ruth-Key) derived from its registry key (RK). BEG registers for the multicast service ID_SVC, which falls under the responsibility of ZKS_A. BEG receives the Broadcast Access Key (BAK) belonging to the multicast service ID_SVC, encrypted using a Temporary Key (TK). In addition, BEG also receives the value TK_RAND, can then calculate the key TK from RK and TK_RAND and therefore decrypt BAK. BEG receives the random values SK_RAND from which it can determine the values of the short-term keys (SK) with the help of BAK. This enables BEG to decrypt the multicast service (content) that is encrypted using these SKs and identified by ID_SVC. The BEG initiates a transfer from the area of responsibility of the ZKS_A to the ZKS_B, in which it sends a transfer request (HORequest = Handover Request) to ZKS_A. This message advantageously contains the identity ID_BEG of the user terminal or ID_USER of the user, the identity ID_ZKS_B of ZKS_B, the identity ID_SVC 'of a multicast service in the area of responsibility of ZKS_B, as well as possibly further relevant data. In favor of the user terminal, ZKS_A sends an access control request (AccessRequest) to ZKS_B, which, in addition to the ID_BEG, ID_USER, ID_SVC 'and ID_ZKS_A identities, may also contain further relevant data. Based on the fact that BEG is already successfully authenticated and registered with ZKS_A, ZKS_B can decide without a renewed authentication and registration of the BEG, whether or not it wants to grant BEG access to the multicast service ID_SVC '. If ZKS_B grants the user terminal access to the desired multicast service ID_SVC ', it sends an access grant message (ACCESSAccept) to ZKS_A together with the MBMS service key MSK belonging to the desired multicast service ID_SVC'. Since ZKS_B the Benut ZCOM_A sends a handover accept message (HO-Accept = Handover Accept) to BEG. This message advantageously contains the identities ID_ZKS_B and ID_SVC 'of the access control server ZKS_B or the desired service. ZKS_A sends to BEG the key MSK that it contained in ZKS_B, encrypted using the temporary key TK. Since BEG knows the key TK, it can decrypt the key MSK. Based on its knowledge of MSK, BEG is now able to decrypt the MSK encrypted MBMS traffic keys (MTKs). The decrypted MTKs now allow the BEG to decrypt the multicast service (Content ') that is encrypted using these MTKs and identified by ID_SVC'.

7 shows another case constellation in which a mobile terminal BEG changes from a 3GPP2 service access network to a DVB-H service access network.

The BEG authenticates itself to the ZKS_A with the help of an authentication key (Ruth-Key), derived from its registry key (RK). BEG registers for the multicast service ID_SVC, which falls under the scope of ZKS_A falls. BEG receives to the multicast service Belonging to ID-SVC Broadcast Access Key (BAK), encrypted with the help of a temporary Keys (TK). Next to it BEG also the value TK_RAND, can then from RK and TK_RAND the key Calculate TK and therefore decode BAK. BEG receives the Random SK_RAND, from which BAK uses the Values of the short-term keys (SK). This is BEG in the Able to decrypt the multicast service (Content) that encrypted with the help of these SKs is and is identified by ID_SVC. The BEG initiates a transfer from the area of responsibility of the ZKS_A to the ZKS_B in which there is a transfer request (HORequest = Handover Request) to ZKS_A. This message contains benefits the identity ID_BEG of the user terminal or ID_USER of the user, the identity ID_ZKS_B of ZKS_B, the identity ID_SVC 'of a multicast service in the area of responsibility from ZKS_B, as well as possibly further relevant data. In favor of of the user terminal sends ZKS_A an access control request (AccessRequest) to ZKS_B, which may be advantageous next to the identities ID_BEG, ID_USER, ID_SVC 'and ID_ZKS_A contains further relevant data. Based on the fact BEG has already successfully authenticated and registered with ZKS_A ZKS_B can without a re-authentication and registration BEGes decide whether to grant BEG access to the multicast service ID_SVC 'or Not. granted ZKS_B the user terminal access to the desired Multicast service ID_SVC, it sends an access grant message (AccessAccept) to ZKS_A along with the service or programs Encryption Key (SEK / PEK) belonging to the desired multicast service ID_SVC '. Because ZKS_B the user terminal BEG access to the desired Granted multicast service ZKS_A sends a transfer grant message (HOAccept = Handover Accept) to BEG. This message advantageously contains the identities ID_ZKS_B and ID_SVC 'of the Access control server ZKS_B or the desired service. ZKS_A sends at BEG the key SEK or PEK, which it received from ZKS_B, encrypted with Temporary key help TK. Since BEG knows the key TK, it can be the key Decrypt SEK or PEK. by virtue of from its knowledge of SEK and PEK, BEG is now in a position to cooperate with SEK or PEK encrypted Decrypt Traffic Encryption Keys (TEKs). The decrypted TEKs now allow the BEG to decrypt the multi-cast service (Content) that encrypted with the help of these TEKs is identified by ID_SVC ' becomes.

8th Figure 11 shows another case constellation in which a mobile terminal switches from a DVB-H service access network to a 3GPP2 service access network.

With the help of its public key certificate, BEG authenticates itself to ZKS_A and registers for the multicast service ID_SVC, which falls under the responsibility of ZKS_A. Since BEG has successfully registered for the multicast service ID_SVC at ZKS_A, ZKS_A sends the service or programs belonging to this service Encryption Key (SEK / PEK) to BEG. In this case, SEK / PEK is contained in a rights object RO and is present there in encrypted form. For encryption the public key K_PUB of BEG is used. With the help of his private device key K_PRIV, BEG can decrypt the key SEK or PEK and thus also the traffic encryption keys (TEK), which are sent encrypted with the help of SEK or PEK to the user terminals. The decrypted TEKs now allow the BEG to decrypt the multicast service (content) that is encrypted using these TEKs and identified by ID_SVC. The BEG initiates a transfer from the area of responsibility of the ZKS_A to the ZKS_B, in which it sends a transfer request (HORequest = Handover Request) to ZKS_A. This message advantageously contains the identity ID_BEG of the user terminal or ID_USER of the user, the identity ID_ZKS_B of ZKS_B, the identity ID_SVC 'of a multicast service in the area of responsibility of ZKS_B, as well as possibly further relevant data. In favor of the user terminal, ZKS_A sends an access control request (AccessRequest) to ZKS_B, the advantage In addition to the identities ID_BEG, ID_USER, ID_SVC 'and ID_ZKS_A, there may also be other relevant data. Based on the fact that BEG is already successfully authenticated and registered with ZKS_A, ZKS_B can decide without a renewed authentication and registration of the BEG, whether or not it wants to grant BEG access to the multicast service ID-SVC '. If ZKS_B grants the user terminal access to the desired multicast service ID_SVC ', it sends an access grant message (ACCESSAccept) to ZKS_A together with the broadcast access key (BAK) belonging to the desired multicast service ID_SVC'. Since ZKS_B has granted the user terminal BEG access to the desired multicast service, ZKS_A sends a Handover Accept (HOAccpt) message to BEG. This message advantageously contains the identities ID_ZKS_B and ID_SVC 'of the access control server ZKS_B or the desired service. ZKS_A sends to BEG the key BEG the key BAK it contained from ZKS_B, encrypted with K_PUB, the public device key of BEG. Since the BEG knows the private device key K_PRIV belonging to K_PUB, it can decrypt BAK. The BEG receives the multicast service identified by ID-SVC and encrypted using short-term keys (SK). In addition to the encrypted multicast service, BEG also receives the unencrypted random values SK_RAND. Using BAK and the random numbers SK_RAND, the BEG can calculate the short-term keys SK and thus decrypt the multicast service (Content ').

In the in the 3 to 8th In the exemplary embodiments illustrated, the user terminal BEG initiates the transfer or the change from the first service access network DZN-A to the second service access network DZN-B. In alternative embodiments, the switch is initiated by the access control server ZKS-A or ZKS_B.

at the illustrated embodiments receives the user terminal BEG first a broadcast service that is in the area of responsibility of the first Access control server ZKS-A falls. This However, this is not mandatory. It is only necessary that the user terminal BEG authenticated at the first access control server ZKS-A and registered.

The Data content of that broadcast or multicast service for which the user terminal BEG is a handover in the area of responsibility of the second access control server ZKS-B wishes, d. H. by ID_SVC` identified broadcast service, can either be the same like the data content belonging to the broadcast service ID_SVC or the belong to another broadcast service. The inventive method can thus be used in two ways, d. H. on the one hand is the change of broadcast access technology not associated with a change at the application level or the Change of broadcast access technology goes hand in hand with a change at the application level.

At the in 3 to 8th In the illustrated embodiments, the access accept messages sent from the second access control server ZKS-B to the first access control server ZKS-A receive the key (MSK, SEK / PEK, BAK) whose knowledge enables the decryption of a broadcast service. Therefore, these messages are preferably protected by suitable measures, for example by encryption against unauthorized interception. Alternatively, the access acknowledge message (Access Accept) may also omit the key (MSK, SEC / PEK or BAK) and instead send an identifier for this key which enables the first access control server ZKS-A to retrieve the associated key from a database in which this key is stored.

These the first service access network DZN-A is a 3GPP service access network, becomes the service-specific key the second access technology, d. H. SEK / PEK at DVB-H 18Crypt and BAK at 3GPP2-BCMSCS directly with the MUK, the subscriber-specific MBMS user key encrypted and to the user terminal BEG sent. Should the scope of the subscriber-specific key MUK will not be extended in this way, then at one Execution form the key MUK only as an input to calculate a new key K used instead of the subscriber-specific key MUK for encryption of SEK / PEK or BRK serves. In one embodiment depends the calculation of the key K from other data, such as the identity of the second Access control server ZKS-B, its IP address and a random number from. One more way to calculate the key provide key-dependent HASH functions represents.

at take over the system according to the invention the access control server ZKS-A, ZKS-B several functions, for example authentication, registration, key distribution, data encryption, receiving and sending messages for delivery of access control functions. These functions are at a alternative embodiment of the system according to the invention not taken from a single server, but you can be distributed to different servers.

By the cooperation of the access control server ZKS-A, ZKS-B, the Controlling access to broadcast services becomes a fast and easy-to-use transition supported by one broadcast access technology to another, without that a participant of a mobile terminal BEG each with each access control server ZKS in its area of responsibility, who wants to receive the broadcast service, re-authenticate and must register.

Claims (22)

Method for continuously transmitting encrypted Data of a broadcast service of service access networks that have different key hierarchies to a mobile terminal (BEG), wherein the mobile terminal (BEG) at a change of a first service access network (DZN-A) from which the mobile terminal (BEG) the data of the broadcast service with a first data content encryption key (MTK; TEK; SK) receives to a second service access network (DZN-B) from which the mobile Terminal (BEG) the data of the broadcast service with a second data content encryption key (MTK; TEK; SK) receives one with a subscriber-specific key (MUK; K-PUB; TK) of the first Service Access Network (DZN-A) Encrypted Key (SEK; PEK; MSK; BAK) of the key hierarchy of the second service access network (DZN-B). The method of claim 1, wherein the subscriber-specific key (MUK; TK) following an authentication of the mobile terminal (BEG) at an access control server (ZKS-A) of the first service access network (DZN-A) is generated. Method according to claim 1, wherein the mobile terminal (BEG) and the access control server (ZKS-A) of the first service access network (DZN-A) both about the subscriber-specific key (MUK; K-PUB; TK). Method according to claim 1, wherein the mobile terminal (BEG) the data of the broadcast service with the first data content encryption key (MTK; TEK; SK) from a first access control server (ZKS-A) of the first Service Access Network (DZN-A) receives encrypted. Method according to claim 1, wherein the mobile terminal (BEG) the data of the broadcast service with the second data content encryption key (MTK; TEK; SK) from a second access control server (ZKS-B) of the second Service access network (DZN-B) receives encrypted. The method of claim 1, wherein the with the subscriber-specific key (MUK; K-PUB; TK) encrypted keys (SEC; PEK; MSK; BAK) from the access control server (ZKS-A) of the first service access network (DZN-A) to the mobile terminal (BEG) transmitted is and by the mobile terminal (BEG) by means of the mobile terminal (BEG) known subscriber-specific Key (MUK; K PRIV; TK) decrypted becomes. Method according to claim 6, wherein the mobile terminal (BEG) by means of the decrypted key (SEC, PEK, MSK, BAK) the second data content encryption key (MTK; TEK; SK) or derives to that of the second access control server (ZKS-B) received with the second data content encryption key (MTK; TEK; SK) To decrypt data from the broadcast service. Method according to claim 1, wherein the mobile terminal (BEG) a change from the first service access network (DZN-A) to the second service access network (DZN-B) from the access control server (ZKS-A) of the first service access network (DZN-A) by means of a request message (HO request) requests. The method of claim 8, wherein the request message (HO request) a subscriber identity, an identity of the access control server (ZKS-B) of the second service access network (DZN-B) and has an identity of the broadcast service. The method of claim 9, wherein the access control server (ZKS-A) of the first service access network (DZN-A) an access request message (Access Request) to the access control server (ZKS-B) of the second Service Access Network (DZN-B) transmits which the participant identity, the identity the broadcast service and an identity of the access control server (ZKS-A) of the first service access network (DZN-A). The method of claim 10, wherein the access control server (ZKS-B) of the second service access network (DZN-B) an access acknowledgment message (Access Accept) to the access control server (ZKS-A) of the first Service Access Network (DZN-A) returns which the participant identity, the identity the broadcast service and a key (SEK, PEK, MSK, BAK) of the key hierarchy of the second service access network (DZN-B). Method according to claim 11, wherein the access control server (ZKS-A) of the first service access network (DZN-A) issues a bill of exchange acknowledgment message (HO-Accept) to the mobile terminal (BEG), which contains an identity of the second access control server (ZKS-B) and an identity of the broadcast service. The method of claim 12, wherein the access control server (ZKS-A) of the first service access network (DZN-A) with the subscriber-specific key (MUK; K-PUB; TK) encrypted key (SEC; PK; MSK; BAK) of the second key hierarchy in a message to the mobile terminal (BEG) transmits. The method of claim 1, wherein the first service access network (DZN-A) through a 3GPP, 3GPP2 or DVB-H service access network is formed. The method of claim 1, wherein the second service access network (DZN-B) through a 3GPP, 3GPP2 or DVB-H service access network is formed. The method of claim 1, wherein the change of the first service access network (DZN-A) to the second service access network (DZN-B) through the access control server (ZKS-A) of the first service access network is performed automatically when the mobile terminal (BEG) from a transmission range of the first service access network (DZN-A) moved out. Method according to claim 1, wherein the mobile terminal (BEG) formed by a mobile phone, a laptop or a PDA device becomes. The method of claim 1, wherein said by the mobile terminal (BEG) received data are formed by multimedia data. System for continuous transmission of encrypted Data of a broadcast service to a mobile terminal (BEG) of service access networks that have different key hierarchies have, with: (a) a first access control server (ZKS-A) a first service access network (DZN-A), which is a first key hierarchy having, wherein the mobile terminal (BEG) the data of the broadcast service with a first data content encryption key (MTK; TEK; SK) from the first access control server (ZKS-A) of the first service access network (DZN-A) encrypted receives; (B) a second access control server (ZKS-B) of a second service access network (DZN-B), which has a second key hierarchy, in which the mobile device (BEG) the data of the broadcast service with a second data content encryption key (MTK; TEK; SK) from the second access control server (ZKS-B) of the second service access network (DZN-B) encrypted receives; (C) the mobile terminal (BEG) when switching from the first service access network (DZN-A) to the second service access network (DZN-B) one with a subscriber-specific key (MUK; K-PUB; TK) of the first service access network (DZN-A) encrypted Key (SEC; PEK; MSK; BAK) of the key hierarchy of the second service access network (DZN-B). The system of claim 19, wherein the subscriber-specific key (MUK; K-PUB; TK) encrypted key (SEC, PK, MSK, BAK) from the first access control server (ZKS-A) of the first service access network (DZN-A) to the mobile terminal (BEG) and through the mobile device (BEG) by means of the mobile terminal (BEG) known subscriber-specific key (MUK; K PRIV; TK) decrypted becomes. The system of claim 20, wherein the mobile terminal (BEG) by means of the decrypted key (SEC, PK, MSK, BAK) the second data content encryption key (MTK; TEK; SK) or derives to that of the second access control server (ZKS-B) received with the second data content encryption key (MTK; TEK; SK) To decrypt data from the broadcast service. Access control server (ZKS) to provide a continuous broadcast service for a mobile terminal (BEG), wherein the access control server (ZKS) when changing the mobile terminal (BEG) from a service access network (DZN) of the access control server (ZKS) to another service access network DZN`) one with a subscriber-specific key (MUK; K-PUB; TK) of the service access network (DZN) encrypted key (SEK; PEK; MSK; BAK) of the second service access network (DZN`) to the mobile terminal (BEG) transfers.